Psychotic disorders are a group of psychiatric disorders characterized by the presence of delusions, hallucinations, bizarre behavior, and disorganized speech. There are several possible causes for the occurrence of psychotic disorders in patients who underwent solid organ transplant, including pre-existing mental illness, electrolyte disturbances, infections of the central nervous system, and adverse reaction to drugs. Calcineurin inhibitors are a class of immunosuppressive drugs, such as tacrolimus and cyclosporine, that are currently considered the mainstay in the immunosuppressive drug regimen of patients who underwent solid organ transplant. Neurotoxicity is one of the adverse reactions associated with the use of calcineurin inhibitors, ranging from upper limb tremors to psychotic disorders and seizures. We report the cases of 2 liver transplant recipients who developed severe psychotic disorder 1 month after the procedure. After an extensive investigation for other possible triggers of psychiatric disease, the use of tacrolimus was considered to be the most likely cause for the acute psychotic disorder. In less than 24 hours after suspension of that drug, all symptoms disappeared in both patients, making a causal relationship with tacrolimus even more likely. The patients were then given cyclosporine, another drug from the same class, allowing for adequate immunosuppression and preserved graft function, with no further psychiatric symptoms. This report confirms that a 24-hour trial of tacrolimus suspension can be safe and effective in the diagnosis of drug-related psychotic disorders in patients who underwent liver transplant. This article is compliant with the Helsinki Congress and the Istanbul Declaration.